The goals of this study are 1) to determine what environmental factors are associated with "somatic mutations" as manifested in chromosome breakage and other evidence of chromosome damage which occurs in those with evidence of embryotoxicity and 2) to investigate the feasibility of a new method of evaluation of chromatid interchanges (using Hoechst 33258 binding) and its applicability to the determination of chromosome damage in the population under study; and, in so doing, to assess the more general applicability of this approach to the monitoring of populations "at risk" which are known to be exposed to possible environmental hazards such as X-irradiation, pesticides, etc. Chromatid interchanges as detected with this method will be correlated with the frequency of chromosome breakage in the population under study as well as with history of exposure to radiation, among other factors.